Research On The Apply Of Rock Asphalt In Road Projects

With the rapid development improvment of China's national economy , more and more high-grade highway will be completed and put into using, Chinese expressway mileage is more than 40,000 km.More than 95 percent of the road surface structure of these high-grade highway used asphalt pavement. On the other hand the majority of urban roads use asphalt pavement too. The use of the highway for more than a year, regardless of the road just a half or flexible pavement, they both have produced a different degree of rutting. All destruction in the asphalt pavement, rutting issue is particularly important, in addition to its impact on travel comfort, but also has a direct impact on traffic safety, such as operating difficulties when changing lanes, rutting stagnant water and high-speed lane Shuipiao or icing, braking difficulties in the harsh climatic conditions. Particularly in the heat summer between 2003 and 2004, there were a number of large areas of serious rutting in many provinces's highway of our country, liwen highway in Jiangxi, Jinliwen highway in Zhejiang, Beijing-Fuzhou highway Jitai area in Shandong, some highways have emerged relatively serious rutting in Fujian and Jiangsu Province, that impact the saft and comfort on traffing.In order to improve the life of the road,and increase the high temperature stability, transport researchers did some studies from many areas, the one is studying the new road structure, such as more gravel asphalt concrete, asphalt Mastic resin mixture ( SMA), large-size gravel mixture of asphalt (LSAM); The other is the introduction of new cement materials (modified asphalt), such as SBS, PE and rock asphalt (NES), and so on. In promoting the use of modified asphalt, for the most part polymer modified asphalt such as SBS, PE,can not compatible with asphalt, construction and poor workability, isolated and high prices limited the promotion of the use of modified asphalt. However, the pilot study found that a natural rock asphalt modifier can substantially increase the resistance of asphalt concrete track performance indicators, and significant increase in the adhesion of asphalt and anti-ageing properties. Then we can dispersed the mixing rock asphalt which through a simple mechanical in the matrix under the condition of heating smash.The internal components of Rock asphalt decided its good road performance, because of its high nitrogen content, the nitrogen content is generally more than asphalt oil 10 times even a few times. The nitrogen element in the natural asphalt existents in the form of functional groups, it has a strong invasive and high resistance of the freedom ; at the same time , mix into the base asphalt when its softening point as high as 230 degrees, it will have good properties of anti- hightemperature and anti-aging; Natural rock asphalt is non-wax,in fact, natural asphalt is not excluding December in the oil state, the content of Sumatra decrease sharply and convert into other form under the influence of the long-term effects of various external media. When it joined the asphalt in the matrix, the property will be transmited to matrix asphalt in the reorganization in certain degree,thereby reducing the harm of Sumatra in December against the asphalt. Join the general natural rock asphalt into the asphalt oil, Because the solvent function of temperature and small molecules, so that natural rock asphalt micellar which has bigger molecular weight ruptured,and breakdown of the micelles exposed many points and these points immediately be filled, saturated by the small molecule material in the ordinary asphalt, formated a new portfolio, eventually formed new approach which the large natural rock asphalt micellar elements as the center, filled with ordinary asphalt small molecules. The essential is added a lot of spontaneous non-core material in the general Asphalt, the molecular weight of the core is bigger than ordinary asphalt molecular weight, Transform the structure of the original base asphalt which the small molecular weight of the asphalt is the core, the extent of change decided by the size of the joined the molecular weight of asphalt and the size of nitrogen, oxygen, the amount of sulfur side chain. The bigger Molecular weight, the higher activity, then this transformation more clear,the modified asphalt technology are also more superior performance.Rock asphalt is easy to dissolve in the base asphalt when 160℃~ 180℃, Blending process and the operation are simple; the reasonable stirring time is 25 min; Considering about the matrix of base asphalt and economic factors, the Suggestion is the add-Asphalt between 5 percent to 10 percent, the specific add-Asphalt decided by the project.Modified asphalt is more stable than base asphalt when high temperature,the temperature susceptibility reduces, the anti-rutting capacity of asphalt mixture under high-temperature has enhanced; Water stability has improved. The cost of modified asphalt paving of the road is same as ordinary road construction. Under normal circumstances, The cost of rock modified asphalt concrete pavement increase five to eight percent compared with ordinary asphalt concrete pavement. According to the data of test road, rock modified asphalt concrete pavement has beter Performance of anti-rutting under high-temperature, and service life is longer than general road, thus analysis under the condition of using of decades-benefit,The economic benefits of rock modified asphalt concrete pavement is Obviously.In particular,due to their service life increased, the direct annual average costs not increased,however it will significantly lower than the general cost of asphalt concrete pavement.In addition because of rocks modified asphalt concrete pavement has a longer service life, to avoid the other costs resulting from the occurrence of disruption of traffic due to road maintenance,so the economic benefits of road-modified is significantly.